%!PS-Adobe-2.0

%%Pages: 8

% --- Part 1.  Make global definitions ------------------------------------------

% builds the path outlining a square with corners
% (0, 0), (s, 0), (s, s), (0, s)

/buildsquare {
  0 0 moveto
  s 0 lineto
  s s lineto
  0 s lineto
  closepath
} def

/a 3 def
/b 4 def
/c a dup mul b dup mul add sqrt def

% find the vertex (x, y)

/x a c div a mul def
/y b c div a mul def

% and some analgous ratios
/X a c div b mul def
/Y b c div b mul def

/N 8 def

/draw-page {


gsave

72 dup scale
1 72 div setlinewidth

2.5 5.5 translate

0.6  dup scale

% --- draw the three squares -------------------------------

/s c def
gsave
-90 rotate
newpath
buildsquare
stroke
grestore

/s a def
gsave
b a atan rotate
newpath
buildsquare
stroke
grestore

/s b def
gsave
c 0 translate
b a atan rotate
newpath
buildsquare
stroke
grestore

% --- the vertical line ------------------------------------------------

newpath
x y moveto
0 y c add neg rlineto
stroke

% --- the red triangle ------------------------------------------------

gsave
A rotate
newpath
0 0 moveto
x y lineto
0 c neg lineto
closepath
gsave
1 0 0 setrgbcolor
fill
grestore
stroke
grestore

% --- the other triangles ------------------------------------------------

newpath
0 0 moveto
y neg x lineto
c 0 lineto
closepath
stroke

newpath
c 0 moveto
c X add Y lineto
0 0 lineto
closepath
stroke

newpath
c 0 moveto
x y lineto
c c neg lineto
closepath
stroke

grestore
showpage

/Helvetica-Bold findfont
16 scalefont
setfont

20 100 moveto
(Euclid's proof of Pythagoras' Theorem) show

} def

% --- Part 2.  Draw, run the loop ------------------------------------------

/A 0 def
/dA 90 N 1 sub div def

%%Page: 1 1
/A 0 def
draw-page 

%%Page: 2 2
/A dA def
draw-page 

%%Page: 3 3
/A dA 2 mul def
draw-page 

%%Page: 4 4
/A dA 3 mul def
draw-page 

%%Page: 5 5
/A dA 4 mul def
draw-page 

%%Page: 6 6
/A dA 5 mul def
draw-page 

%%Page: 7 7
/A dA 6 mul def
draw-page 

%%Page: 8 8
/A dA 7 mul def
draw-page